Cancer : class of diseases characterized by out-.of-control cell growth in the body

There are over 100 different types of cancer, and each is classified by the type of cell that is,initially affected.Cancerous cells are also called malignant cells Antigen: An antigen is any substance that causesthe immune system to produce antibodies .against it An antigen may be a foreign substance from the environment such as chemicals, bacteria, or.viruses

  An antigen may also be formed within the body,as with bacterial toxins or tissue cells

.Antigenic substance produced in cancer cells Normal proteins in the body are not antigenic thus any protein that is not exposed to the immune system triggers an immune response Exp‘ of -proteins that are normally produced in extremely small quantities, or proteins that are normally produced only in certain stages.of development The body‘s own immune system is able to specifically distinguish between normal and cancer cells by recognizing cancer antigensdisplayed on the tumor cell‘s surface

Classification of cancer antigens is basedon their molecular structure and source.Among the cancer antigens- some may be tumor specific (PSA-prostate

specific antigen )

while others may also be expressed by normal tissues “cancer associated antigen”

(Cancer antigen 125-is the most important cancer associated).

Differentiation antigen - a molecule expressed by one particular tissue-type, and also by cancer cells derived.from that tissue-type

For example, the tyrosinase and Melan-A/MART-1 antigens: are expressed in normal skin melanocyte cells, and in most.melanomas, but not other cell types in the bodyMutation and splice variant antigens - alterations in the DNA sequence of a gene frequently result in differences in the gene‘s protein sequence when the mutation alters one or more amino acids in the protein. An alteration in the messenger RNA (mRNA) sequence, may cause the mRNA to be spliced differently, producing different forms of the.protein

For example, the NY-CO-38 antigen has four splice variants,.each of which has a different tissue expression

Over expressed /antigen - a protein that is over expressed in a cancer cell compared to a normal cell. For example normal epidermal growth factor receptor (EGFR) can be distinguished by a specific targeted antibody when over.expressed

CT antigens - proteins expressed only in normal ’germ line‘ tissues (testis, placenta, and embryonic and fetal ovary) and in cancer cells. Because germ line cells do not express major histo-compatibility complex (MHC) molecules, the cells are unable to present antigens on their surface, thus .a cancer therapy would not target these normal cells The NY-ESO-1 antigen: it is expressed in testis, in a variety of tumors such as melanoma, breast, ovary, prostate,.bladder, sarcoma, and lung

Viral antigens – viral proteins are expressed in infected human cells and these viral proteins, or the peptide fragments resulting from the processing of the proteins, are presented.to, and recognized by, the immune system

Cancer markers:most are found in low levels in healthy personsused to stage cancer, to indicate a prognosis, to monitor treatment,

or in follow-up to watch for cancer recurrence.Some cancer markers are associated with many types of cancer.Once cancer is diagnosed, cancer marker levels sometimes help to

determine the extent of cancer. Higher levels can indicate more advanced cancer and a worse prognosis in some cases.

The patient and their physician may use this information to choose between more or less aggressive treatments.

Depending upon the cancer marker, it can be measured in blood, urine, stool or tissue. Some widely used cancer markers include: AFP, CA 15-3, CA 19-9, CA 125, CEA..

Alphafetoprotein(AFP):Germ cell tumors& hepato cellular carcinoma.

Carcinoembryonic antigen: (CEA)bowel cancers, Occasional lung or breast cancer.

CA-125:Ovarian cancer.MUC-1:breast cancer.epithelial tumor antigen:(ETA)breast cancer.Tyrosinase : malignant melanoma, normally present in minute

quantities greatly elevated levels in melanoma.

Melanoma-associated antigen (MAGE)malignant melanoma ,also.normally present in the testis CA19-9- as a screening test for cancer,.particularly pancreatic cancerCa 72-4-gastric cancer PSA-prostate specific antigen is a protein produced by cells of the prostate gland in.man

Cancer Antigen Tests Cancer antigen tests are tests for proteins, carbohydrates, and hormones that serve as markers for cancer. These markers can be found in different fluids and tissues of the body. Antigen tests are done with blood, urine, occasionally with other body fluids, and tissue samples. When a cancer antigen test comes back positive, the antigen was found. Although a positive result does not mean that the cancer is present, it does mean that there is a greater chance of havingthat cancer1

Gastrointestinal Cancer Antigen Tests Tumor M2-PK Colo-rectal, stomach, pancreas, esophagus, breast,cervical, and skin CA 19-9Pancreas (most common), liver, colon, non-malignant

CEA Colorectal (predominant in combination with CA195) along with markers for stomach, pancreas, lung, breast, and medullary thyroid

CA 72-4StomachExist also gender ,lung, bone categories of cancers*. antigens

An antibody ,known as an immunoglobulin, is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen.

In most cases, interaction of the B cell with a T-helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding.

.Antigens triggers an immune response in the host Tumor antigens are useful in identifying tumor cells and.are potential candidates for use in cancer therapy The role of these antigens is to attract antibody targets for diagnostic and therapeutic applications, because it hes antibodies may enable early detection of the tumor, in many cases antibody binding to tumor cells leads to destruction of these cells through a process known as antigen-dependent cellular cytotoxicity the antibody can be conjugated to a "payload" such as a toxin which is targeted to the cancer cell by the antibody and thus kills the cancer cell but spares.normal cells

http://www.panomics.com/index.php?id=product_25/http://www.ncbi.nlm.nih.gov/books/NBK13896http://www.antibody.com/index2.htmlhttp://clincancerres.aacrjournals.org/content/15/17/5323.fullhttp://medical-dictionary.thefreedictionary.com/Tumor+markers